This invention relates to a new nickel coating composition to protect electronic equipment such as computers, video games or the like as well as cathode ray tubes, oscilloscope tubes or the like from electromagnetic interference (EMI). More particularly, this invention relates to a new nickel dispersion coating composition useable as a shielding coating that maintains high electrical conductivity even after exposure to elevated temperatures and humidity during operation. The new coating composition of this invention may be applied as a one-coat air dry system that is spray applied and needs no protective overcoat. It also, of course, may be applied by other means such as brushing, dipping, roller coating, or the like, and may also be overcoated with a decorative finish.
The state of its art is indicated by the following U.S. Pat. Nos. 3,968,056; 3,390,104; 3,920,452; 3,412,043; 2,280,135; 4,305,847; and 4,382,981.
It has generally been known that metal particles, such as copper, silver, gold platinum and the like, dispersed in a binder resin material or solution can be used to make an electrically conductive coating. However, all of these prior coatings have suffered from various deficiencies. Copper, for example, oxidizes during storage or use and the electrical properties of the coating are detrimentally effected. The use of silver, gold or platinum as the conductive material in sufficient quantity to insure good electrical conductivity greatly increases the cost of the electrically conductive coating.
The demands for conductive compositions are significantly increasing with increased emphasis on performance characteristics such as durability under harsh environmental changes; ability to use these compositions at increased temperatures; greater abrasion resistance and the like. At the same time, greater product capabilities and, perhaps more importantly, lower processing costs have been sought.
Accordingly, a main object of this invention is to provide a new coating composition containing finely divided nickel particles which is suitable for use in forming applied coatings having very good electrical conductance properties, and which composition is considerably more economical to produce than prior coatings having similar performance characteristics.
Another important object of this invention is to provide a new nickel coating composition which when applied as a coating maintains high electrical conductivity even after exposure to heat, humidity or other harsh environmental conditions.
Another object of the invention is to provide a new nickel coating composition that includes a special additional pigment component.
Another object of this invention is to provide an environmentally stable coating composition that is relatively economical to produce without significantly sacrificing electrical conductance properties of the coating composition.
A still further object of this invention is to provide a new coating composition capable of forming EMI shielding coatings on enclosures for electronic equipment.
An additional object of this invention is to provide a new composition with desirable magnetic properties.
Other objects, features and advantages of the present invention will become apparent from the subsequent description and the appended claims.